Heat sensitive device



Nov. 24, 1942. B. cYR

HEAT SENSITIVE DEVICE Filed July 5, 1941 30 l'l Fig.3

. mu m W 1 L N i .U

Patented Nov. 24, 1942 UNITED STATES PATENT OFFICE 2,302,665 HEAT SENSITIVE DEVICE Benjamin Cyr, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application July 5, 1941, Serial No. 401,200

15 Claims.

The present invention is directed to devices which are responsive to changes in temperature,

and particularly double metal ribbon devices of the type disclosed in the copending application of lgzllis H. Gille, Serial No. 401,205, filed July 5, 1 1.

One of the main objects of this invention is to design a device along the lines of the Gille device but with greater sensitivity to the appearance and disappearance of direct heat radiations. This is accomplished by adding slip friction in the connections so that the contact device is operated immediately upon a reversal in movement of the two legs of the double ribbon.

Another object is to design a double ribbon temperature responsive device in which the tension in the two legs may be readily equalized when the device is being assembled.

A still further object is to design a device of the above type in which the two legs are normally maintained under tension and which has a manual means for temporarily relieving the tension so that the ribbon may slip with respect to the support and .bring the two legs to equal tension when tension is again applied to them.

These and other objects will readily become apparent as the following specification is read in the light of the accompanying drawing, in which:

Figure l is a side sectional view of a device involving my invention and taken along the line l--i of Figure 2;

Figure 2 is a rear elevation of the device, parts being shown in section for the sake of clarity;

Figure 3 is a detail view of the mounting lever;

Figure 4 is a side elevation of a modified form of my device, the lower portion being shown in section;

Figure 5 is a detail view of the roller on which the double ribbon of Figure 4 is supported;

Figure 6 is a detail view of the friction mounting for the roller shown in Figure 5;

Figure '1 is a side section of a third modification of my invention, and

Figure 8 discloses an oil burner for producing combustion within a furnace and one manner in which my device may be mounted in the wall of the furnace.

Referring now to Figure l, the reference numeral It indicates 'a channel shaped supporting member having a pair-oi projections, one of which is shown at II in Figure 1, at one end thereof which are received in complementary depressions l2 in a mounting lever II. By means of this arrangement the mounting lever is may which the two legs I9 and 29 are adapted to pass.

rotate about the projections ii. The mounting lever I3 is in the form of a U having a pair of legs I5 located on opposite sides of the supporting member to.

A thin metallic strip in the form of a double ribbon indicated generally at it is supported across the base of the mounting lever l3 and a small projection ll on the lever I3 extends through a small hole in the ribbon to prevent it from slipping with respect to the lever ii. The ribbon is bent double to form a pair of expansible legs l9 and 20 whose ends are bent into a channel shaped member 2|. The ends are retained in this member by means of a clamping plate 22" and screw 23.

A resilient tensioning plate 24 is carried at each end by the channeled supporting member l0 and has an opening 25 in its middle portion through which a screw 28 loosely extends. The stem of the screw 26 enters a tapped hole in the member 2| and by rotating the screw 28 in a clockwise direction the member 2| may be drawn upwardly and the two legs i9 and 20 placed under tension. v

Referring now to the sectioned portion of Figure 2, the reference numeral 28 indicates a cup-shaped member having an annular channeled portion which receives an annular graphite friction washer 29 which is adapted to bear against the le is provided with a center opening which receives screw 30 which in turn passes through the slot 32 in leg 15, which permits rotation of lever is. Screw 30 enters a tapped hole 3| in the member in. A sleevev 32 surrounds the stem of the screw so and is or such length that when the screw 39 is tightened the cup 28 will bring the friction washer 29 into frictional/ engagement with the leg I! of the lever is but will not clamp this lever against the support Hi. In other words the friction is due only to leg II bearing outwardly against the graphite washer 29. A mounting identical to the one just described is provided on the other leg II of the lever ll. These two friction mountings resist the rotation 01 the lever I! about the projection ii but will permit such rotation upon the development of a predetermined force due to the diflerential ex-' pansion between the two legs is and 29. This action will be described more in detail later.

An actuating 'rod 94 is provided with an enlarged head 35 having a slot 98 therein through These two legs are provided with small notches,

I5 of the lever IS. The cup 2'8 fit in order that the head 35 of the actuating rod 34 will be supported thereby. It will be noted with reference to Figure 1 that the depth of the slot 36 is such that the two legs l9 and 20 are pulled inwardly from their straight line position. Without this restriction they would normally assome a straight line position due to the tension exerted on them by the tensioning spring 24. When the leg l9 expands due to an increase in its temperature, the tension therein is released with the result that the tension in the leg 20 will cause this leg to move towards its straight line position, thereby moving the actuating rod 34 and leg I 9 to the left. This principle of operation is exactly the same as that disclosed in the copending application of Willis H. Gille, Serial No. 401,205 referred to in the objects of this in vention.

Bracket 38 and bracket 39 are both insulatingly carried on the supporting member HI and are insulated from each other, being mounted by means of screws 40. The bracket 38 adjustably carries a stationary contact 4| and the bracket 39 adjustably carries a stationary contact 42. Each bracket is provided with a terminal screw 43 for connecting the stationary contacts with an external circuit. Bracket 44 is also mounted on the support It! by means of screws 45 and this bracket carries a movable contact arm 45 by means of a resilient hinge 41. The movable contact arm 46 carries at its free end a pair of movable contacts 4B and which are adapted to alternately engage the two stationary contacts 4| and 42 respectively. The mid portion of this contact arm is provided with an opening 50 through which the actuating rod 34 is adapted to extend. The connection between the actuating rod 34 and the contact arm 46 is by means of a bowed leaf spring 49, one end of which is secured to the contact arm 46 and the other end of which engages a small opening in the end of the actuating rod 34. This spring tends to move the contact arm 45 toward the right (Figure 1) with respect to the rod 34 and thus maintains it against a shoulder, indicated by reference numeral 52, on the rod 34.

The purpose of this is to eliminate any lost motion between rod 34 and contact arm 45 upon reversal in movement of the rod 34.

When the two expanslble legs i9 and 20 are at substantially the same temperature, they will be in the position shown in Figure 1 and the contact M will be in engagement with the stationary contact 43!. When heat is applied to the leg I! it will expand and relieve the tension therein, at which time the tension in the leg 20 will cause this leg to straighten and move the actuating rod 34 toward the left. The shoulder 55 on the actuating rod 34 will now engage contact arm 45 and force the contact 48 into engagement with the stationary contact 42. This occurs after only a slight movement of the leg 20 and after the engagement of the contact 48 with the stationary contact 42 further movement or the actuaing rod will be impossible. In order to accommodate a further straightening of the leg 23, the slip friction mountings composed oi. the elements 28 to 32 have been provided which will now permit the leg 20 to swing its lower end and lever l3 toward the right. as seen in Figure 1. thus further straightening the leg 25.

When the heat is removed from the leg ll, it will rapidly come to the same temperature as the leg 20, in which case the leg I! will move in a direction toward its straight line position and will pull the actuating rod 34 toward the right. 75

The rod 34 through the bowed leaf spring 43 will move the contact 5| into engagement with the stationary contact 4|. Further movement of the rod will then be'resisted by means of this spring 49 but any further tendency of the leg I! to straighten and return to the position shown in Figure 1 will result in the lever 13 being rotated in a clockwise direction as permitted by the slip friction mountings.

It will be seen therefore that this device is extremely sensitive in that the very first movement of the two legs I! and 20 due to their differential expansion causes an actuation of the switching mechanism and that any additionalmovement results in a slippage of the mounting lever l3. Upon a reversal in temperature change the first movement of the legs is and 23 will again cause actuation of the switching mechanism and a further movement will be accommodated by the slippage of the lever II.

A slight modification of the above arrangement is disclosed in Figure 4. In this figure, the lever i3 has been replaced by a roller 55 which is fixed to an axle 56. The axle 56 extends through openings 51 in the opposite side of the channel shaped supporting member i 0. This modification is provided with a resilient tensioning plate 24 in the same manner as the modification shown in Figure 1, whereby the two legs 19 and 20 are always under tension and exert an upward force on the roller 55. It will be noted in connection with Figure 6 that the openings 51 are not round but are more or less oval shaped with the result that the axle 56 engages the sides of these openings in two places indicated at 58 and 55. There is, therefore, no tendency of this axle to move laterallyas it rotates. Moreover, the sliding friction between the axle 55 and the sides of the opening 51 normally resists rotation of the roller 55 and this rotation takes place only after the actuation of the contact mechanism by the actuating rod 34. This occurs in the same manner as described in connection with Figure 1, and a further description here is not believed necessary.

There is a possibility that after a long period of disuse and after a number of temperature variations this mechanism might possibly get out of step and for this reason a manual reset lever 60 is provided with an up-turned end 5| which engages beneath a lip 52 formed on the supporting member ID. The lever has a bearing surface 63 which engages the center portion of the tension spring 24, so that whenthe right-hand end of this lever 53 is depressed the spring 24 is bent inwardly and the tension on the two legs l8 and 20 is relieved. At this time, therefore, the ribbon 16 will slip with respect to the roller and equalize the tension in the two legs I! and 20. When the manual lever 50' is released the two legs I9 and 20 will be under equal tension and the contact arm will be in engagement with the proper stationary contact. The device will then be in a condition to function properly.

Figure 7 shows a further modification of this invention in which the roller 55 is fixed with respect to the supporting member N. The slip friction in this case is provided between the actuating rod 34 and the contact arm 45. This slip friction comprises an opening in the contact arm 45 through which the actuating arm 34 extends. This opening is provided with an inlet 55 which carries a pairof spring blades 55 and 51 which are biased into engagement with that portion of the actuating rod 34 which extends through the opening in the contact arm 45. The friction beasoaoos I r 3 tweenthe blades 6' and ll in the actuating rod elongated heatexpansible member bent double I4 is suiiicient for the contact arm 48 to be actuto form a pair of substantially parallel expansible ated by means of the rod 34, but after the conlegs, means placing said legs under tension theretacts SI or l! have moved into engagement with by tending to make them assume straight line. either of the stationary contacts 4| or 4! respec- 5 positions, a movably mounted actuating rod havtively, then further diiferential expansion being means acting between said two legs and forctween the two legs l9 and 20 will be taken care ing them out of their straight line position whereof by the rod 34 slipping with respect to the conby said actuating rod will be moved upon a diiIertact arm it. Here again, therefore, the switchential expansion of said legs, a movable contact ing mechanism will be actuated as a resultof the 10 am, stationary contact means cooperable there-' initial differential expansion between the two legs with, and impositive driving means between said l9 and 2|] in each direction, and therefore a det tin r d'and said contact arm whereby relavice is provided which is extremely sensitive. t m ent may take place between said actu- It might be explained that the upper ends of ating rod and contact am after said stationary the two legs I! and are mounted in a slightly 5 t t means ha b e ag d,

d e e t manner in F e 7 than in the mOdl- 3. In a device of the character described, an

iications shown in Figures 1 and 2. In this case, elongated heat expansible member bent double the ends of these legs are bent into a supporting t form a pair of substantially parallel expansible member I! and clamped therein by means of 9. legs, ns placing said legs under te si wherelampin p ate T s clamping plate s 20 by they tend to assume straight line positions, a ported by means of two screws 12 which extend movably mounted actuating rod having means loos ly t u h op nin s in a tenslonins plate acting between said two legs and forcing them out to provide the proper tension on the two legs I! of th ir traight line position whereby said actuand 20. ating rod will be moved upon a differential ex- .Figure 8 merely shows the conventional oil pansion of i l stationary contact means, u e 15 for Producing fl in the a movable contact moved by said actuating rod bustion chamber of a furnace, one wall of which t ngagement with aid stationary contact is shown'in section at 11. The device of my inmeans, and slip friction means providing for convention may be mounted in a casing It and positinued movement of aid other leg toward straight tioned in opening 79 in the Wall of the furnace line position after said movable contact has enin such a manner that the leg I! is positioned to gazed said tationary contact means.

absorb radiant heat from the flame I6. Posi- In a device of th character described, a tioned in this manner, it will be. seen that the leg thin metamc ribbon t double to form a pair I! protects or shields the leg 20 from direct heat A of ub tantially parallel expansi'ble legs, means radiations. For this reason, when combustion is placing said 1 d r tension whereby they tend present within the furnace the leg I! will be at to assume trai ht line positions, a movably a higher temperature than the leg 20 and theremounted actuating d havi g a slightly enfore the leg I! will be expanded with respec to larged head at one end, a slot in said head through i the leg 20 and the contact arm 48 will be in enwhich both legs of Said d uble ribbon pass, said gagement with the stationary contact 4-2. .Upon head and ribbon having inter-fitting portions by disappearance of the flame the two legs I! and means f which id h ad i supported by said 20 will rapidly come to the same temperature and ribbon, the depth if i l t being such that said the parts will return to the position shown in less are pulled inwardly from their straight line Figures 1, 4 and 7, depending upon which modipositions whereby id actuating rod' will be flcation is being usedr moved u n a differential expansi n of d 8 This invention has been described in connecand a 32, device t t b id od. tion with an oil burner control system so that it In adevice of t character described, a thin will respond to the radiant heat 01 combustion, n t d bl form a ir of but it will be readily appreciated that there are figm gm a ibfglegs, mean s placmany other adaptations. For example, an elec- 50 Sald legs under t i whereby they tend trical heating winding may be wrapped directly to assume straight line iti ns, a movably about the leg I! in order that the switch contact mounted tuating d having a slightly enlarged l2 mightbe engaged upon the application of heat head at one end 1 g i aid h a through to the leg I! and the contact ll engaged when which both legs said i m i b ass, said no heat is applied thereto- 5 head and ribbon having interfltting p r i ns by Many other changes and modifications in this means of wmch said head is supported b said invention will doubtless occur to those who are ribbon the depth of said 1 1; being uch that said skilled in the art, and I therefore wish it to be legs are pulled inwardly from th ir traight line understood that I am to be limited only by the positions whereby said actuating rod will be scope of the appended claims and not by the moved upon a differential expansion of said legs,

v specific embodiments disclosed. v v movable contact arm, stationary contact means I claim as my invention: eooperable therewith, and imposltive driving 111 device of the character described, at means between said actuating rod and said conelongated heat expansible member bent double to tact arm whereby relative movement may take rm a pa of substantially pa a xna s as place between said actuating rod and contactarm 685, means P g said legs under tension thereafter said stationary contact means has been en- -by tending to make them assume straight line p0- gaged. i i a movably m n d tua in rod having 6. In a device of the character described, a thin means' act be Said two legs and forcing metallic ribbon bent double to form a pair of th m u of their ht lin p i i n wh e y TU substantially parallel expansible legs, means lacsaid actuating rod will be moved upon a diil'erening said legs under tension whereby they tend to tial expansion of said legs, and a rotatably mountassume straight line positions, a movably mounted arm actuated by said rod for operating a coned actuating rod having a slightly enlarged head trol device. at one end, a slot in said head through which I 2. In a device of the character described, an bothless of said double ribbon pass, said head and ribbon having interfitting portionsby means of which said head is supported by said ribbon, the depth of said slot being such that said legs are pulled inwardly from their straight line positions whereby said actuating rod will be moved upon a differential expansion of said legs, a movable contact arm, stationary contact means cooperable therewith, and slip friction means providing for continued movement of said other leg toward its straight line position after said contact arm has been stopped by said stationary contact means.

'7. In a device of the character described, a

supporting member, a mounting member rotatably mounted on said supporting member, a double ribbon temperature responsive device comprising a pair of substantially parallel expansible legs mounted at one end on said mounting member, a resilient member supporting the other end of said legs and maintaining them under tension whereby they tend to assume a straight line position, means carried by said legs and holding them out of their straight line position whereby said legs will move laterally upon a differential expansion thereof, a control device movable a limited distance by said legs, and slip friction means between said rotatable mounting member and said supporting member which provides for said legs first actuating said control device through its limited movement and then rotates about said supporting member to permit said other leg to continue to move toward its straight line position as said one leg continues to expand.

8. In a device of the character described, a supporting member, a U shaped mounting member rotatably mounted at the bend of the U on said supporting member, a double ribbon temperature responsive device comprising a pair of substantially parallel expansible legs mounted at one end on said mounting member, a resilient member supporting the other end of said legs and maintaining them under tension whereby they tend to assume a straight line position, means carried by said legs and holding them out of their straight line position whereby said legs will move laterally upon a differential expansion thereof, a control device movable a limited distance by said legs, and slip friction means located between the legs of the U of said U shaped mounting member and said supporting member which provides for said legs first actuating said control device through its limited movement and then rotates about said supporting member to permit said other leg to continue to move toward its straight line position as said one leg continues to expand.

9. In a device of the character described, a supporting member, a roller frictionally journaled in said supporting member, a thin metallic ribbon bent double across said roller to form a pair of substantially parallel expansible legs, resilient means supporting the ends of said legs and placing them under tension thereby tending to make them assume straight line positions, means carried by said legs holding them out of their straight line positions whereby said legs move laterally upon a differential expansion thereof, and a control device movable a limited distance by said legs, said roller slipping with respect to said supporting member to permit further movement of said other leg after said control device has been moved to a limit position.

10. In a device of the character described, a supporting member, a roller frictionally journnlnri in said simpolting member, a thin metallic ribbon bent double across said roller to form a pair of substantially parallel expansible legs, resilient means supportin the ends of said legs and placing them under tension thereby tending to make them assume straight line positions, means carried by said legs holding them out of their straight line positions whereby said legs move laterally upon a differential expansion thereof, a control device movable a limited distance by said legs, said roller slipping with respect to said supporting member to permit further movement of said other leg after said con-- trol device has been moved to a limit position, and means for manually relieving the tension in said legs whereby said ribbon may slip with respect to said roller to equalize the tension in said legs.

11. In a device of the character described, a supporting member, a mounting member having a rounded mounting surface carried by said supporting member, a thin metallic ribbon bent double across said mountin member and engaging said rounded surface, said ribbon forming two substantially parallel expansible legs, a tensioning plate carried by said supporting member, means connecting the ends of said ribbon to said tensioning plate whereby it maintains said legs under tension, means carried by said legs holding them out of their straight line positions whereby said legs move laterally upon a diiferential expansion thereof, a control device actuated by said legs, and a lever rotatably mounted on said supporting member and engaging said tensioning plate whereby said plate may be manually depressed to relieve the tension in said two legs and permit said ribbon to slide on the mounting member and equalize the tension in said legs.

12. In a device of the character described, a

double ribbon temperature responsive device comprising a pair of substantially parallel expansible legs, means maintaining said legs under tension whereby they tend to assume straight line positions, an actuating member, one end of which is carried by said legs, said one end holding said legs out of their straight line positions, a movable contact arm, stationary contact means engageable by said arm, a slip friction connection between saidactuating member and said arm, and means for heating one of said legs whereby it expands and said other leg moves toward its straight line position and moves said actuating member, said slip friction connection permitting further movement of said other leg after said contact arm has engaged said stationary contact means.

13. In a device of the character described, a double ribbon temperature responsive device comp sin p r of substantially parallel expansible legs, means maintaining said legs under tension whereby they tend to assume straight line positions, an actuating member, one end of which is carried by said legs, said one end holding said legs out of their straight line positions, a rotatably mounted contact arm, a Pair of oppositely disposed stationary contacts alternately engageable by said contact arm, an opening in said arm through which the other end of said actuating member extends, a pair of resilient fingers carried by said contact arm and frictionally engaging said actuating member to form a slip friction connection, and means for heating one of said legs whereby it expands and sai other leg moves toward its straight line position and moves said actuating member, said slip friction connection permitting further movement of said asoaeoe other leg after said contact arm has engaged said stationary contact means.

14. In a device of the character described comprising in combination, an elongated flexible metallic member bent double to form a pair of heat expansible legs. means supporting said legs and placing them under tension whereby they tend to assume straight line positions, an actuatingmember having means acting on at least one of said legs forcing it out 0! its straight line position, whereby upon a differential expansion of said legs the tension in said one leg changes causing said leg to move said actuating member, a control device, and a slip friction connection between said actuating member and said control device. v

15. In a device 0! the character described comprising in combination, an elongated flexible metailic member bent double to form a pair oi heat expansible legs, means supporting said legs and placing them under tension whereby they tend to assume straight line, positions, an actuating member having means acting on at least one of said legs forcing it out of its straight line position, whereby upon a difierential expansion of said legs the tensionjin said one leg changes causing said leg to move said actuating member, stationary contact means, a rotatably mounted contact arm, a movable contact carried thereby for cooperation with ,said stationary contact means, and means connecting said actuating member and said contact arm including a slip iriction device .wherebyadditional movement of said one leg is permitted after said movable contact has been actuated.

BENJAMIN CYR. 

